A recent study showed gut microbes present in a diet with fish oil, once transplanted, protected mice on diets rich in lard against weight gain and inflammation normally associated with diets that include unhealthy fats.

"We were surprised that the lard and the fish oil diet, despite having the same energy content and the same amount of dietary fiber--which is the primary energy source for the gut bacteria--resulted in fundamentally different gut microbiota communities and that the microbiota per se had such large effects on health," study author Robert Caesar said.